A transformer is an electrical device that transfers energy between two or more circuits through the phenomenon of electromagnetic induction. Transformers are commonly used to increase (step-up) or decrease (step-down) the voltages of alternating current in electric power applications. This is accomplished by passing a varying current through the primary winding to generate a magnetic flux in the transformer's core. This flux then induces a voltage in the transformer's secondary winding. Depending on the ratio of the primary windings to the secondary windings, the transformers output voltage can be increased or decreased.
For most transformers designed for small-scale use, such as in devices commonly used in homes or offices, one of two styles of transformers is typically used. These are transformers with either an E-I laminate or a toroidal core (See FIG. 1). In a laminate transformer utilizing an E-I structure, the matching “E” and “I” components are stamped from sheets of thin grain oriented electrical steel, and the sheets are then stacked to create the core. Typically, the primary and secondary windings are wound on bobbins. Multiple bobbins are placed on spindles and spun in order to apply the windings. This method of winding the core with wire supplied on bobbins allows for automation, and so reduces the manufacturing times and also provides insulation between the windings and the core. The E-I core laminations are stacked inside the bobbins to complete the transformer.
In the case of a toroidal core, the core element is typically made from a continuous strip of silicon steel, which is wound like a tight clock spring. The ends are tacked into place with small spot welds, to prevent the coiled steel from unwinding. The core is typically insulated with an epoxy coating or a set of caps or multiple wraps of insulating film, such as MYLAR and/or NOMEX (MYLAR and NOMEX are registered trademarks, reg. no. 0559948 and 86085745, respectively, of the E. I. De Pont de Nemours and Company Corporation, a Delawar Corporation located at 1007 Market Street, Wilmington, Del. 19898). The transformer's windings are applied directly onto the insulated core itself. Additional insulation is required to isolate the windings. Since the windings must be wound through the center hole of the core and the core is one piece, bobbins can't be used on toroidal transformers.
As they do not lend themselves to automation, toroidal transformers are more labor intensive to produce. However, the continuous strip of steel used in the core allows the toroidal transformer to be smaller, lighter, more efficient, and quieter than its E-I laminate counterpart. These qualities are highly desirable in many applications and justify the additional expense.
Thus, there is a need for a toroidal transformer that enjoys the advantages of be smaller size, lighter weight, increased efficiency, and quieter operation while overcoming the drawbacks of being labor intensive and more expensive to produce. The present novel technology addresses these needs.